You do not have a chance to gain this extra Rage when using attacks that are separate from the swing timer. This means that attacks such as Mortal Strike, Bloodthirst, Whirlwind, and damage dealt from Sweeping Strikes do NOT have a chance to generate extra Rage. However, attacks such as Heroic Strike and Cleave do have a chance to gain extra Rage. In the case of Cleave, it is possible that both targets may generate the extra Rage.

As of patch 2.0.10 Unbridled Wrath now has an increased chance to grant rage when using slower weapons. The proc chance is 3 PPM per talent point based on base weapon speed. Here's a rank table with popular weapon speeds: